Polymerized in-situ hybrid solid ion-conductive compositions

ABSTRACT

Provided herein are methods of forming solid-state ionically conductive composite materials that include particles of an inorganic phase in a matrix of an organic phase. The methods involve forming the composite materials from a precursor that is polymerized in-situ after being mixed with the particles. The polymerization occurs under applied pressure that causes particle-to-particle contact. In some embodiments, once polymerized, the applied pressure may be removed with the particles immobilized by the polymer matrix. In some implementations, the organic phase includes a cross-linked polymer network. Also provided are solid-state ionically conductive composite materials and batteries and other devices that incorporate them. In some embodiments, solid-state electrolytes including the ionically conductive solid-state composites are provided. In some embodiments, electrodes including the ionically conductive solid-state composites are provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 15/662,116, filed Jul. 27, 2017, now U.S. Pat. No.9,926,411, which claims the benefit of priority to U.S. ProvisionalPatent Application No. 62/467,022, filed Mar. 3, 2017 and to U.S.Provisional Patent Application No. 62/534,135, filed Jul. 18, 2017, eachof which is incorporated by reference in its entirety and for allpurposes.

FIELD OF INVENTION

The invention relates generally to the field of solid-state alkali-ionand alkali metal batteries. More particularly, it relates to ionicallyconductive composite materials and battery components, such aselectrolytes and electrodes, that incorporate the ionically conductivecomposite materials.

BACKGROUND

Solid-state electrolytes present various advantages over liquidelectrolytes for primary and secondary batteries. For example, inlithium ion secondary batteries, inorganic solid-state electrolytes maybe less flammable than conventional liquid organic electrolytes.Solid-state electrolytes can also facilitate use of a lithium metalelectrode by resisting dendrite formation. Solid-state electrolytes mayalso present advantages of high energy densities, good cyclingstabilities, and electrochemical stabilities over a range of conditions.However, there are various challenges in large scale commercializationof solid-state electrolytes. One challenge is maintaining contactbetween electrolyte and the electrodes. For example, while inorganicmaterials such as inorganic sulfide glasses and ceramics have high ionicconductivities (over 10⁻⁴ S/cm) at room temperature, they do not serveas efficient electrolytes due to poor adhesion to the electrode duringbattery cycling. Another challenge is that glass and ceramic solid-stateconductors are too brittle to be processed into dense, thin films. Thiscan result in high bulk electrolyte resistance due to the films beingtoo thick, as well as dendrite formation, due to the presence of voidsthat allow dendrite penetration. The mechanical properties of evenrelatively ductile sulfide glasses are not adequate to process theglasses into dense, thin films. Improving these mechanical propertieswithout sacrificing ionic conductivity is a particular challenge, astechniques to improve adhesion, such as the addition of a solid polymerbinder, tend to reduce ionic conductivity. It is normal to observe morethan an order of magnitude conductivity decrease with as little as 1 wt% of binder introduced. Solid-state polymer electrolyte systems may haveimproved mechanical characteristics that facilitate adhesion andformation into thin films, but have low ionic conductivity at roomtemperature.

Materials that have high ionic conductivities at room temperature andthat are sufficiently compliant to be processed into thin, dense filmswithout sacrificing ionic conductivity are needed for large scaleproduction and commercialization of solid-state batteries.

SUMMARY

The compositions, methods and devices of the present invention each haveinventive aspects. One aspect of the invention relates to a solid-stateelectrolyte composition. The solid-state electrolyte includes ionicallyconductive inorganic particles in a non-ionically conductive polymermatrix, wherein the non-ionically conductive polymer matrix includes across-linked polymer network, and wherein the composition has an ionconductivity of at least 1×10⁻⁴ S·cm⁻¹. In some embodiments, theionically conductive inorganic particles are at least 50% by weight ofthe composition. In some embodiments, the non-ionically conductiveorganic matrix includes a polymer binder. In some embodiments, thepolymer binder may be between 1-5% by weight of the composition. In someembodiments, the polymer matrix is free of polymer binder.

In some embodiments, the non-ionically conductive polymer matrix is2.5%-60% by weight of the composition. In some embodiments, thenon-ionically conductive polymer matrix is at least 20% by weight of thecomposition. In some embodiments, the ionically conductive inorganicparticles are sulfide glass particles. In some embodiments, thenon-ionically conductive polymer matrix is polymerized in-situ. In someembodiments, the cross-linked polymer network includes a backboneselected from a polyolefin, a polysiloxane, a perfluoropolyether,polystyrene, and a cyclic olefin polymer. In some embodiments, thecross-linked polymer network includes a polydimethylsiloxane (PDMS)backbone. In some embodiments, the cross-linked polymer network includesa polybutadiene (PBD) backbone. In some embodiments, the cross-linkedpolymer network includes a cured epoxy resin. In some embodiments, thecross-linked polymer network includes urea-urethane groups, urethanegroups, or thiourethane groups. In some embodiments, the cross-linkedpolymer network includes a poly(urethane), a poly(ureaurethane),poly(thiourethane), a poly(acrylate), a poly(methacrylate), apoly(maleimide), poly(acrylamide), a poly(methacrylamide), a polyolefin,or a polystyrene.

In some embodiments, the composition includes one or more unreactedreactants or byproducts of a polymerization reaction. In someembodiments, the unreacted reactant includes isocyanate functionalgroups. The isocyanate functional groups may be blocked. In someembodiments, the unreacted reactant includes one or more of an aminefunctional group, an alcohol functional group, a thiol functional group,and a blocked isocyanate. In some embodiments, the unreacted reactantincludes one or more functional cross-linkers. In some embodiments, theunreacted reactant includes a radical initiator. In some embodiments,the unreacted reactant includes functional groups selected from one ormore of: an acrylic functional group, a methacrylic functional group, anacrylamide functional group, a methacrylamide functional group, astyrenic functional group, an alkenyl functional group, an alkynylfunctional group, a vinyl functional group, allyl functional group, anda maleimide functional group. In some embodiments, the unreactedreactant includes functional groups selected from one or more of: epoxyresins, oxiranes, glycidyl groups, and alkene oxides.

In some embodiments, wherein the cross-linked polymer network includesone or more linking groups selected from:—CH₂CH(H/CH₃)(R) where R═—C(O)—O—,—C(O)—NR—,—C₆H₄—, or  1)

—NH—C(O)—NR—, where R is H,alkyl or aryl;  2)—NH—C(O)—O—; and  3)—NH—C(O)—S—.  4)

Another aspect of the invention relates to a battery including an anode;a cathode; and a solid-state electrolyte including ionically conductiveinorganic particles in a non-ionically conductive polymer matrix,wherein the non-ionically conductive polymer matrix includes across-linked polymer network, and wherein the composition has an ionconductivity of at least 1×10⁻⁴ S·cm⁻¹.

Another aspect of the invention relates to a method of forming asolid-state ionically conductive composition. The method includesproviding a mixture of polymer matrix precursors and ionicallyconductive inorganic particles; initiating polymerization of the polymermatrix precursors while applying a pressure of at least 10 MPa to themixture to form a polymer matrix; and after polymerizing the polymermatrix precursors, releasing the applied pressure.

In some embodiments, the polymer matrix precursors and the ionicallyconductive inorganic particles are mixed in a solution. In someembodiments, the solution is cast on a substrate to form a film prior toinitiating polymerization of the polymer matrix precursors. In someembodiments, the film is dried prior to initiating polymerization of thepolymer matrix precursors. In some embodiments, initiatingpolymerization of the polymer matrix precursors includes heating thepolymer matrix precursor. In some embodiments, the method furtherincludes mixing a thermal radical initiator with the polymer matrixprecursors and the ionically conductive inorganic particles. In someembodiments, the polymer matrix precursors include polymer matrixprecursors functionalized with a first type of functional group andpolymer matrix precursors functionalized with a second type offunctional group, the first type of functional group being reactive withthe second type of functional group. In some embodiments, one or both ofthe first and second types of functional groups are blocked. In someembodiments, the polymerization is addition polymerization. In someembodiments, the polymerization is ring opening polymerization. In someembodiments, polymerizing the polymer matrix precursors includescross-linking. In some embodiments, initiating polymerization of thepolymer matrix precursors includes exposing the polymer matrixprecursors to ultraviolet radiation. In some embodiments, thepolymerization is radical polymerization

In some embodiments, the mixture of polymer matrix precursors andionically conductive inorganic particles is a dry mixture. In someembodiments, the method further includes extruding the mixture ofpolymer matrix precursors and ionically conductive inorganic particles.

In some embodiments, applying pressure increases the ionic conductivityof the composite by a factor of at least two. The increase ionicconductivity may be maintained after releasing the applied pressure.

In some embodiments, providing a mixture of polymer matrix precursorsand ionically conductive inorganic particles includes a first in-situpolymerization to form linear polymers. In some such embodiments,wherein polymerizing polymer matrix precursors comprises cross-linkingthe linear polymers. The first in-situ polymerization may be performedat a first temperature lower than the temperature of the cross-linking.According to various embodiments, the first polymer in-situpolymerization may be performed prior to applying pressure to themixture or while applying pressure to the mixture.

Another aspect of the invention relates to a method including mixingpolymer matrix precursors and ionically conductive inorganic particles;optionally polymerizing the polymer matrix precursors to formpolymerized linear polymers; initiating cross-linking of one or both ofthe polymer matrix precursors and polymerized linear polymers whileapplying a pressure of at least 10 MPa to the mixture to form a polymermatrix; and after cross-linking, releasing the applied pressure.

In some embodiments, the method includes polymerizing the polymer matrixprecursors to form linear polymers prior to applying the pressure. Insome such embodiments, cross-linking includes cross-linking the linearpolymers.

In some embodiments, the polymer matrix precursors include di-functionalpolymer matrix precursors and tri-functional cross-linking agents. Thetri-functional cross-linking agents may include blocked isocyanategroups. In some embodiments, the di-functional polymer matrix precursorsare polymerized to form linear polymers prior to cross-linking.

In some embodiments, applying pressure increases the ionic conductivityof the composite by a factor of at least two. The increase ionicconductivity may be maintained after releasing the applied pressure.

Another aspect of the invention relates to an ionically conductivecomposite material that includes ionically conductive inorganicparticles in a non-ionically conductive polymer matrix, wherein thecomposition has an ion conductivity of at least 1×10⁻⁴ S·cm⁻¹. In someembodiments, the ionically conductive inorganic particles are at least50% by weight of the composition. In some embodiments, the non-ionicallyconductive organic matrix includes a polymer binder. In someembodiments, the polymer binder may be between 1-5% by weight of thecomposition. In some embodiments, the polymer matrix is free of polymerbinder.

In some embodiments, the non-ionically conductive polymer matrix is2.5%-60% by weight of the composition. In some embodiments, thenon-ionically conductive polymer matrix is at least 20% by weight of thecomposition. In some embodiments, the ionically conductive inorganicparticles are sulfide glass particles. In some embodiments, thenon-ionically conductive polymer matrix is polymerized in-situ. In someembodiments, the polymer network includes a backbone selected from apolyolefin, a polysiloxane, a perfluoropolyether, polystyrene, and acyclic olefin polymer. In some embodiments, the polymer network includesa polydimethylsiloxane (PDMS) backbone. In some embodiments, the polymernetwork includes a polybutadiene (PBD) backbone. In some embodiments,the polymer network includes a cured epoxy resin. In some embodiments,the polymer network includes urea-urethane groups, urethane groups, orthiourethane groups. In some embodiments, the polymer network includes apoly(urethane), a poly(ureaurethane), poly(thiourethane), apoly(acrylate), a poly(methacrylate), a poly(maleiamide),poly(acrylamide), a poly(methacrylamide), a polyolefin, or apolystyrene.

In some embodiments, the composition includes one or more unreactedreactants or byproducts of a polymerization reaction. In someembodiments, the unreacted reactant includes isocyanate functionalgroups. The isocyanate functional groups may be blocked. In someembodiments, the unreacted reactant includes one or more of an aminefunctional group, an alcohol functional group, a thiol functional group,and a blocked isocyanate. In some embodiments, the unreacted reactantincludes one or more functional cross-linkers. In some embodiments, theunreacted reactant includes a radical initiator. In some embodiments,the unreacted reactant includes functional groups selected from one ormore of: an acrylic functional group, a methacrylic functional group, anacrylamide functional group, a methacrylamide functional group, astyrenic functional group, an alkenyl functional group, an alkynylfunctional group, a vinyl functional group, allyl functional group, anda maleimide functional group. In some embodiments, the unreactedreactant includes functional groups selected from one or more of: epoxyresins, oxiranes, glycidyl groups, and alkene oxides.

In some embodiments, wherein the polymer network includes one or morelinking groups selected from:—CH₂CH(H/CH₃)(R) where R═—C(O)—O—,—C(O)—NR—,—C₆H₄—, or  1)

—NH—C(O)—NR—, where R is H,alkyl or aryl;  2)—NH—C(O)—O—; and  3)—NH—C(O)—S—.  4)

Another aspect of the invention relates to a battery including an anode;a cathode; and a solid-state electrolyte including ionically conductiveinorganic particles in a non-ionically conductive polymer matrix,wherein the non-ionically conductive polymer matrix includes a polymernetwork, and wherein the composition has an ion conductivity of at least1×10⁻⁴ S cm⁻¹.

Another aspect of the invention relates to a method of forming asolid-state ionically conductive composition. The method includesproviding a mixture of polymer matrix precursors and ionicallyconductive inorganic particles; initiating polymerization of the polymermatrix precursors while applying a pressure of at least 10 MPa to themixture to form a polymer matrix; and after polymerizing the polymermatrix precursors, releasing the applied pressure.

In some embodiments, the polymer matrix precursors and the ionicallyconductive inorganic particles are mixed in a solution. In someembodiments, the solution is cast on a substrate to form a film prior toinitiating polymerization of the polymer matrix precursors. In someembodiments, the film is dried prior to initiating polymerization of thepolymer matrix precursors. In some embodiments, initiatingpolymerization of the polymer matrix precursors includes heating thepolymer matrix precursor. In some embodiments, the method furtherincludes mixing a thermal radical initiator with the polymer matrixprecursors and the ionically conductive inorganic particles. In someembodiments, the polymer matrix precursors include polymer matrixprecursors functionalized with a first type of functional group andpolymer matrix precursors functionalized with a second type offunctional group, the first type of functional group being reactive withthe second type of functional group. In some embodiments, one or both ofthe first and second types of functional groups are blocked. In someembodiments, the polymerization is addition polymerization. In someembodiments, the polymerization is ring opening polymerization. In someembodiments, polymerizing the polymer matrix precursors includescross-linking. In some embodiments, initiating polymerization of thepolymer matrix precursors includes exposing the polymer matrixprecursors to ultraviolet radiation. In some embodiments, thepolymerization is radical polymerization.

Another aspect of the invention relates to a solid-state electrode foruse in an alkali ion or alkali metal battery that includes an inorganicphase comprising an ionically conductive amorphous inorganic material,an electrochemically active material, and an electronically conductiveadditive; and an organic phase comprising a non-ionically conductivepolymer matrix. In some embodiments, the non-ionically conductivepolymer matrix is crosslinked. In some embodiments, theelectrochemically active material is selected from lithium cobalt oxide(LCO), lithium manganese oxide (LMO), lithium nickel cobalt aluminumoxide (NCA), lithium iron phosphate (LFP) and lithium nickel cobaltmanganese oxide (NCM). In some embodiments, the electrochemically activematerial is selected from carbon-containing material, asilicon-containing material, a tin-containing material, lithium, or alithium alloyed metal. The solid-state electrode may be a cathode or ananode according to various embodiments. In some embodiments, theelectrode may be in contact with a solid-state electrolyte as describedabove to form an electrolyte-electrode bilayer.

Another aspect of the invention relates to a method of forming anionically conductive composite including mixing polymer matrixprecursors and ionically conductive inorganic particles and initiatingcross-linking in the mixture to form a polymer matrix, whereincross-linking increases the ionic conductivity by a factor of at leasttwo. In some embodiments, the cross-linking is performed under anapplied external pressure of at least 10 MPa. The cross-linking may beperformed under an ambient pressure.

These and other aspects are described further below with reference tothe Figures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 provides a schematic example of formation of a cross-linkednetwork formed by radical polymerization according to certainembodiments of the invention.

FIG. 2 provides schematic examples of formation of a linear polymer anda cross-linked polymer network by addition polymerization according tocertain embodiments of the invention.

FIG. 3 provides schematic examples of formation of a linear polymer andcross-linked polymer networks by ring-opening polymerization accordingto certain embodiments of the invention.

FIG. 4a provides an example of a schematic depiction of a cast filmincluding ionically conductive inorganic particles in a polymer matrixundergoing in-situ polymerization according to certain embodiments ofthe invention to cross-link the polymer chains under applied pressure.

FIG. 4b provides an example of a schematic depiction of a cast filmincluding ionically conductive inorganic particles in a polymer matrixundergoing in-situ polymerization according to certain embodiments ofthe invention to cross-link the polymer chains without applied pressure.

FIG. 5 is a differential scanning calorimetry (DSC) thermogram of4,4-diisocyanatodiphenylmethane blocked with diisopropylamine (MDI-DIPA)in a method of synthesizing of a composite material via in-situpolyurethane formation according to certain embodiments of theinvention.

FIG. 6 is a thermogravimetric curve of MDI-DIPA from obtained fromthermogravimetric analysis (TGA) in a method of synthesizing of acomposite material via in-situ polyurethane formation according tocertain embodiments of the invention.

FIG. 7 is a DSC thermogram of a mixture of polymerizable componentsMDI-DIPA and HLBH2000 obtained in a method of synthesizing of acomposite material via in-situ formation according to certainembodiments of the invention.

FIG. 8 shows DSC traces of pure Li₂S:P₂S₅=75:25 glass (upper trace) anda composite, according to certain embodiments of the invention, of thesame sulfide glass, HLBH2000, and MDI-DIPA, before heat treatment (lowertrace).

FIG. 9 shows DSC traces of a composite film according to certainembodiments of the invention treated at 100° C. and 140° C.

FIG. 10 is a thermogravimetric curve of four samples: pure sulfideglass, a non-treated composite thin film, a composite film according tocertain embodiments heated at 100° C., and a composite film according tocertain embodiments treated at 140° C.

FIG. 11 is a plot shown a) film density before and after cross-linkingcomposites according to certain embodiments under pressure and b)conductivities of pressed composites according to certain embodimentsmeasured at 0 in-lbs and 60 in-lbs.

FIG. 12 shows DSC traces of pure Li₂S:P₂S₅=75:25 sulfide glass and acomposite formed from the sulfide glass, isophoronediisocyanate-diisopropylamine (IPDI-DIPA), and poly[(phenylisocyanate)-co-formaldehyde] (PPFI-DIPA) before and after in-situpolymerization of a polyruethane matrix of the composite.

FIG. 13 shows magnified DSC traces of the composite of FIG. 12 beforeand after thermal crosslinking at 140° C.

FIG. 14 shows examples of polymers that may be in an organic matrix of acomposite material according to certain embodiments.

FIGS. 15-17 show examples of schematics of cells according to certainembodiments of the invention.

DETAILED DESCRIPTION

One aspect of the present invention relates to ionically conductivesolid-state compositions that include ionically conductive inorganicparticles in a matrix of an organic material. The resulting compositematerial has high ionic conductivity and mechanical properties thatfacilitate processing. In particular embodiments, the ionicallyconductive solid-state compositions are compliant and may be cast asfilms.

Another aspect of the present invention relates to batteries thatinclude the ionically conductive solid-state compositions describedherein. In some embodiments of the present invention, solid-stateelectrolytes including the ionically conductive solid-state compositionsare provided. In some embodiments of the present invention, electrodesincluding the ionically conductive solid-state compositions areprovided.

Particular embodiments of the subject matter described herein may havethe following advantages. In some embodiments, the ionically conductivesolid-state compositions may be processed to a variety of shapes witheasily scaled-up manufacturing techniques. The manufactured compositesare compliant, allowing good adhesion to other components of a batteryor other device. The solid-state compositions have high ionicconductivity, allowing the compositions to be used as electrolytes orelectrode materials. In some embodiments, ionically conductivesolid-state compositions enable the use of lithium metal anodes byresisting dendrites. In some embodiments, the ionically conductivesolid-state compositions do not dissolve polysulfides and enable the useof sulfur cathodes.

Further details of the ionically conductive solid-state compositions,solid-state electrolytes, electrodes, and batteries according toembodiments of the present invention are described below.

The ionically conductive solid-state compositions may be referred to ashybrid compositions herein. The term “hybrid” is used herein to describea composite material including an inorganic phase and an organic phase.The term “composite” is used herein to describe a composite of aninorganic material and an organic material.

In some embodiments, the composite materials are formed from a precursorthat is polymerized in-situ after being mixed with inorganic particles.The polymerization may take place under applied pressure that causesparticle-to-particle contact. Once polymerized, applied pressure may beremoved with the particles immobilized by the polymer matrix. In someimplementations, the organic material includes a cross-linked polymernetwork. This network may constrain the inorganic particles and preventsthem from shifting during operation of a battery or other device thatincorporates the composite.

The resulting composite has high conductivity values close to theconductivity of the pristine solid-state ion conductor particles. Theresult is highly conducting, dense, and compliant material which can beeasily processed to desired shapes. “Pristine” refers to the particlesprior to incorporation into the composite. According to variousembodiments, the material has at least half, at least 80%, or at least90% of the ionic conductivity of the particles.

In some embodiments, the polymerization may cause particle-to-particlecontact without applied external pressure. For example, certainpolymerization reactions that include cross-linking may lead tosufficient contraction that particle-to-particle contact and highconductivity is achieved without applied pressure during thepolymerization.

The polymer precursor and the polymer matrix are compatible with thesolid-state ionically conductive particles, non-volatile, andnon-reactive to battery components such as electrodes. The polymerprecursor and the polymer matrix may be further characterized by beingnon-polar or having low-polarity. The polymer precursor and the polymermatrix may interact with the inorganic phase such that the componentsmix uniformly and microscopically well, without affecting at least thecomposition of the bulk of the inorganic phase. Interactions can includeone or both of physical interactions or chemical interactions. Examplesof physical interactions include hydrogen bonds, van der Waals bonds,electrostatic interactions, and ionic bonds. Chemical interactions referto covalent bonds. A polymer matrix that is generally non-reactive tothe inorganic phase may still form bonds with the surface of theparticles, but does not degrade or change the bulk composition of theinorganic phase. In some embodiments, the polymer matrix maymechanically interact with the inorganic phase.

The term “number average molecular weight” or “M_(n)” in reference to aparticular component (e.g., a high molecular weight polymer binder) of asolid-state composition refers to the statistical average molecularweight of all molecules of the component expressed in units of g/mol.The number average molecular weight may be determined by techniquesknown in the art such as, for example, gel permeation chromatography(wherein M_(n) can be calculated based on known standards based on anonline detection system such as a refractive index, ultraviolet, orother detector), viscometry, mass spectrometry, or colligative methods(e.g., vapor pressure osmometry, end-group determination, or protonNMR). The number average molecular weight is defined by the equationbelow,

$M_{n} = \frac{\Sigma\; N_{i}M_{i}}{\Sigma\; N_{i}}$wherein M_(i) is the molecular weight of a molecule and N_(i) is thenumber of molecules of that molecular weight.

The term “weight average molecular weight” or “M_(w)” in reference to aparticular component (e.g., a high molecular weight polymer binder) of asolid-state composition refers to the statistical average molecularweight of all molecules of the component taking into account the weightof each molecule in determining its contribution to the molecular weightaverage, expressed in units of g/mol. The higher the molecular weight ofa given molecule, the more that molecule will contribute to the M_(w)value. The weight average molecular weight may be calculated bytechniques known in the art which are sensitive to molecular size suchas, for example, static light scattering, small angle neutronscattering, X-ray scattering, and sedimentation velocity. The weightaverage molecular weight is defined by the equation below,

$M_{w} = \frac{\Sigma\; N_{i}M_{i}^{2}}{\Sigma\; N_{i}M_{i}}$wherein ‘M_(i)’ is the molecular weight of a molecule and ‘N_(i)’ is thenumber of molecules of that molecular weight. In the description below,references to molecular weights of particular polymers refer to numberaverage molecular weight.

The term “alkyl” as used herein alone or as part of another group,refers to a straight or branched chain hydrocarbon containing any numberof carbon atoms and that include no double or triple bonds in the mainchain. “Lower alkyl” as used herein, is a subset of alkyl and refers toa straight or branched chain hydrocarbon group containing from 1 to 4carbon atoms. The terms “alkyl” and “lower alkyl” include bothsubstituted and unsubstituted alkyl or lower alkyl unless otherwiseindicated. Examples of lower alkyl include methyl, ethyl, n-propyl,iso-propyl, n-butyl, iso-butyl, tert-butyl, and the like.

The term “aryl” as used herein refers to groups that include monocyclicand bicyclic aromatic groups. Examples include phenyl groups.

Inorganic Phase

The inorganic phase of the composite materials described herein conductsalkali ions. In some embodiments, it is responsible for all of the ionconductivity of the composite material, providing ionically conductivepathways through the composite material.

In some embodiments, the inorganic phase is a particulate solid-statematerial that conducts alkali ions. In the examples given below, lithiumion conducting materials are chiefly described, though sodium ionconducting or other alkali ion conducting materials may be employed.According to various embodiments, the materials may be glass particles,ceramic particles, or glass ceramic particles. The solid-statecompositions described herein are not limited to a particular type ofcompound but may employ any solid-state inorganic ionically conductiveparticulate material, examples of which are given below.

In some embodiments, the inorganic material is a single ion conductor,which has a transference number close to unity. The transference numberof an ion in an electrolyte is the fraction of total current carried inthe electrolyte for the ion. Single-ion conductors have a transferencenumber close to unity. According to various embodiments, thetransference number of the inorganic phase of the solid electrolyte isat least 0.9 (for example, 0.99).

The inorganic phase may be an oxide-based composition, a sulfide-basedcomposition, or a phosphate-based composition, and may be crystalline,partially crystalline, or amorphous. In certain embodiments, theinorganic phase may be doped to increase conductivity. Examples of solidlithium ion conducting materials include perovskites (e.g.,Li_(3x)La_((2/3)-x)TiO₃, 0≤x≤0.67), lithium super ionic conductor(LISICON) compounds (e.g., Li_(2+2x)Zn_(1-x)GeO₄, 0≤x≤1; Li₁₄ZnGe₄O₁₆),thio-LISICON compounds (e.g., Li_(4x)A_(1-y)B_(y)S₄, A is Si, Ge or Sn,B is P, Al, Zn, Ga; Li₁₀SnP₂S₁₂), garnets (e.g. Li₇La₃Zr₂O₁₂,Li₅La₃M₂O₁₂, M is Ta or Nb); NASICON-type Li ion conductors (e.g.,Li_(1.3)Al_(0.3)Ti_(1.7) (PO₄)₃), oxide glasses or glass ceramics (e.g.,Li₃BO₃—Li₂SO₄, Li₂O—P₂O₅, Li₂O—SiO₂), sulfide glasses or glass ceramics(e.g., 75Li₂S-25P₂S₅, Li₂S—SiS₂, LiI—Li₂S—B₂S₃) and phosphates (e.g.,Li_(1-x)Al_(x)Ge_(2-x)(PO₄)₃(LAGP), Li_(1+x)Ti_(2-x)Al_(x)(PO₄)).Further examples include lithium rich anti-perovskite (LiRAP) particles.As described in Zhao and Daement, Jour J. Am. Chem. Soc., 2012, 134(36), pp 15042-15047, incorporated by reference herein, these LiRAPparticles have an ionic conductivity of greater than 10⁻³ S/cm at roomtemperature.

Examples of solid lithium ion conducting materials include sodium superionic conductor (NASICON) compounds (e.g., Na_(1+x)Zr₂Si_(x)P_(3-x)O₁₂,0<x<3). Further examples of solid lithium ion conducting materials maybe found in Cao et al., Front. Energy Res. (2014) 2:25 and Knauth, SolidState Ionics 180 (2009) 911-916, both of which are incorporated byreference herein.

Further examples of ion conducting glasses are disclosed in Ribes etal., J. Non-Cryst. Solids, Vol. 38-39 (1980) 271-276 and Minami, J.Non-Cryst. Solids, Vol. 95-96 (1987) 107-118, which are incorporated byreference herein.

According to various embodiments, an inorganic phase may include one ormore types of inorganic ionically conductive particles. The particlesize of the inorganic phase may vary according to the particularapplication, with an average diameter of the particles of thecomposition being between 0.1 μm and 500 μm for most applications. Insome embodiments, the average diameter is between 0.1 μm and 100 μm. Insome embodiments, a multi-modal size distribution may be used tooptimize particle packing. For example, a bi-modal distribution may beused. In some embodiments, particles having a size of 1 μm or less areused such that the average nearest particle distance in the composite isno more than 1 μm. This can help prevent dendrite growth.

The inorganic phase may be manufactured by any appropriate method. Forexample, crystalline materials may be obtained using different syntheticmethods such as sol-gel and solid state reactions. Glass electrolytesmay be obtained by mechanical milling as described in Tatsumisago, M.;Takano, R.; Tadanaga K.; Hayashi, A. J. Power Sources 2014, 270,603-607, incorporated by reference herein.

In certain embodiments, the inorganic phase is an amorphous glassmaterial rather than a crystalline glass-ceramic material. For certainformulations of the solid-state composition, conductivity issignificantly improved by use of an amorphous glass material. This isbecause crystalline and semi-crystalline ionically conductive particlescan have anisotropic conductive paths, whereas amorphous materials haveisotropic conductive paths. In some embodiments in which crystalline andsemi-crystalline ionically conductive particles are used, sintering maybe used to increase ionic conductivity.

Organic Phase

The organic matrix contains one or more types of polymers and may alsobe referred to as a polymer matrix. In some embodiments, the organicmatrix may contain individual polymer chains without significant or anycross-linking between the polymer chains. In some embodiments, theorganic matrix may be or include a polymer network characterized bynodes connecting polymer chains. These nodes may be formed bycross-linking during polymerization. In a cross-linked network, at leastsome of the nodes connect at least three chains. The organic matrix isformed by polymerization of a precursor in-situ in a mixture with theinorganic ionically conductive particles. The polymers of the organicmatrix may be characterized by a backbone and one or more functionalgroups.

The organic matrix polymers have polymer backbones that arenon-volatile. The polymer backbones do not interact too strongly withthe inorganic phase, and may be characterized as non-polar or low-polar.In some embodiments, non-polar components are characterized by having adielectric constant of less than 3 at all frequencies and low-polarcomponents are characterized by having a dielectric constant between 3and 5 at low frequency (60 Hz) and room temperature. In the descriptionherein, polarity of a functionalized polymer component is determined byits backbone. For example, a non-polar polymer may have a non-polarlinear polydimethylsiloxane (PDMS) backbone that is functionalized withpolar end groups. Examples of non-polar backbones include polysiloxanes,polyolefins, polystyrene, and cyclic olefin polymers (COPs).

A COP is a polymer molecule or chain that includes multiple cyclicolefin monomers (e.g., norborene). COPs include cyclic olefin copolymers(COCs), which are produced by copolymerization of a cyclic olefinmonomer with a monomer such as ethylene. Polyolefins include one, two,or more different olefin (C_(n)H_(2n)) monomers and only carbon andhydrogen as well as fully or partially saturated derivatives thereof.

Highly polar polymers such as polyvinylacetate and polyethylene oxide(PEO), are not effective polymer backbones as they may interact toostrongly with the inorganic phase. Polymers that require highly polarsolvents (e.g., polyvinylidene fluoride (PVDF)) may not be appropriate,as such solvents are incompatible with inorganic particles such assulfide glasses.

For certain polymer classes such as polyvinyl, polyacrylamide,polyacrylic, and polymaleimide polymers, the polarity is highlydependent on the identity of their constituent monomers. While some suchpolymers (e.g., polyvinylacetate) may be too polar, it is possible thatless polar polymers in these classes (e.g., poly(dodecyl-n-vinyl ether)may be used as backbones. Further, in some embodiments, these polymerclasses may be included in a copolymer backbone along with a non-polarpolymer (e.g., a polyolefin).

In some embodiments, the glass transition temperature of the polymerbackbone is relatively low, e.g., less than about −50° C., less thanabout −70° C., less than about −90° C., or lower. In some embodiments,the polymer is an elastomer.

Specific examples of polymer backbones include PDMS (T_(g) of −125° C.)and polybutadiene (PBD) (T_(g) of −90° C. to −111° C.). Further examplesinclude styrene butadiene rubbers (SBRs) (T_(g) of −55° C.), ethylenepropylene rubbers (EPRs) (T_(g) of −60° C.), and isobutylene-isoprenerubbers (IIRs) (T_(g) of −69° C.). The glass transition temperatures asprovided herein are examples and may vary depending on the particularcomposition and/or isomeric form of the polymer. For example, the glasstransition temperature of PBD can depend on the degree of cis, trans, orvinyl polymerization.

In some embodiments, the organic phase is substantially non-ionicallyconductive, with examples of non-ionically conductive polymers includingPDMS, PBD, and the other polymers described above. Unlike ionicallyconductive polymers such as PEO, polypropylene oxide (PPO),polyacrylonitrile (PAN), poly(methyl methacrylate) (PMMA), which areionically conductive because they dissolve or dissociate salts such asLiI, non-ionically conductive polymers are not ionically conductive evenin the presence of a salt. This is because without dissolving a salt,there are no mobile ions to conduct in the organic phase.

Another class of polymers that may be used as backbones of the organicmatrix polymers are perfluoropolyethers (PFPEs). A PFPE is aperfluorinated polymer molecule or chain including two or more ethergroups. Examples include but are not limited to backbones such asdifluoromethylene oxide, tetrafluoroethylene oxide, hexafluoropropyleneoxide, tetrafluoroethylene oxide-co-difluoromethylene oxide,hexafluoropropylene oxide-co-difluoromethylene oxide, ortetrafluoroethylene oxide-co-hexafluoropropyleneoxide-co-difluoromethylene oxide and combinations thereof. See, e.g.,U.S. Pat. No. 8,337,986, which is incorporated by reference herein forits teachings thereof. As described in Compliant glass-polymer hybridsingle ion-conducting electrolytes for lithium ion batteries, PNAS,52-57, vol. 113, no. 1 (2016), incorporated by reference herein, PFPEsare single ion-conductors for lithium in the presence of a salt.

Crystalline polymer backbones may also be characterized in terms ofmelting temperature Tm. Crystalline backbones may have a meltingtemperature less than about room temperature in some embodiments. Insome embodiments, if the composite is heat processed (as describedbelow), the melting temperature may be higher, e.g., less than 150° C.,less than 100° C., or less than 50° C. For example, PDMS (Tm of −40° C.)may be preferred in some embodiments over polyethylene (PE; Tm of 120°C. to 180° C.) as the former is liquid at lower temperatures. Meltingtemperatures as provided herein are examples and may vary depending onthe size, particular composition and/or isomeric form of the polymer.Melting temperatures of PBD, for example, vary significantly on thedegree of cis, trans, or vinyl polymerization.

The polymers of the polymer matrix may be homopolymers or copolymers. Ifcopolymers are used, both or all of the constituent polymers of thecopolymers have the characteristics described above (non-volatile,non-polar or low-polar, etc.). Copolymers may be block copolymers,random copolymers, or graft copolymers.

The presence of the organic matrix in a relatively high amount (e.g.,2.5-60 wt % of the solid composites) can provide a composite materialhaving desirable mechanical properties. According to variousembodiments, the composite is soft and can be processed to a variety ofshapes. In addition, the organic matrix may also fill voids in thecomposite, resulting in the dense material.

The organic matrix may also contain functional groups that enable theformation of polymerization in an in-situ polymerization reactiondescribed below. Examples of end groups include cyano, thiol, amide,amino, sulfonic acid, epoxy, carboxyl, or hydroxyl groups. The endgroups may also have surface interactions with the particles of theinorganic phase.

Polymer Precursors and In-Situ Polymerization

According to various embodiments, in-situ polymerization is performed bymixing ionically conductive particles, polymer precursors and anybinders, initiators, catalysts, cross-linking agents, and otheradditives if present, and then initializing polymerization. This may bein solution or dry-pressed as described later. The polymerization may beinitiated and carried out under applied pressure to establish intimateparticle-to-particle contact.

The polymer precursors may be small molecule monomers, oligomers, orpolymers. The polymerization reaction may form individual polymer chainsfrom the precursors (or form longer polymer chains from polymericprecursors) and/or introduce cross-links between polymer chains to forma polymer network. A polymer precursor may include functional groups thenature of which depends on the polymerization method employed.

The polymer precursor may be any of the above polymer backbonesdescribed above (e.g., polysiloxanes, polyvinyls, polyolefins, PFPE's,COP's, or COC's, or other non-polar or low-polar polymers havingrelatively low T_(g)) or constituent monomers or oligomers thereof.Depending on the polymerization method, the polymer precursor may be aterminal- and/or backbone-functionalized polymer.

The reactivity of ionically conductive inorganic particles (and sulfideglasses in particular) presents challenges for in-situ polymerization.The polymerization reaction should be one that does not degrade thesulfide glass or other type of particle and does not lead touncontrolled or pre-mature polymerization of the organic components. Inparticular, glass sulfides are sensitive to polar solvents and organicmolecules, which can cause degradation or crystallization, the latter ofwhich may result in a significant decrease in ionic conductivity.Methods employing metal catalysts are also incompatible withsulfide-based ionic conductors. The high content of the sulfur mayresult in catalyst poisoning, preventing polymerization. As such,methods such as platinum-mediated hydrosilation used for silicon rubberformation, may not be used.

Three methods that may be employed with appropriate selection ofreaction chemistries are radical polymerization, condensationpolymerization, and ring-opening polymerization. These are describedbelow.

Free Radical Polymerization

Free radical polymerization can be employed using a broad range offunctional polymers and small molecules, as it proceeds in presence of avariety of unsaturated bonds, including (meth)acrylates,(meth)acrylamides, alkenes, alkynes, vinyl groups, and allyl groups.Free radical polymerization can be triggered on demand using externalstimuli to generate radicals from initiators. For example, atemperature-initiated radical polymerization can be applied underpressure to freeze the ionically conductive inorganic particles inplace. The radical polymerization method involves a mixture ofpolymerizable components (also called polymer precursors) and a radicalinitiator. Free radical polymerization may also be referred to aschain-growth polymerization.

The radical initiator may be a thermally activated initiator (referredto as thermal initiator) or a photo-activated initiator (referred to asa photo-initiator). In some embodiments, the radical initiator is anorganic azo initiator or a peroxide.

Organic azo initiators include, but are not limited to,2,2′-azobis(isobutylnitrile), 2,2′-azobis(2,4-dimethylpentanenitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylpropanenitrile), 2,2′-azobis(methylbutyronitrile),1,1′-azobis(cyclohexanecarbonitrile), and 1,1′-azobis(cyanocyclohexane).Peroxides include, but are not limited to, benzoyl peroxide, decanoylperoxide, lauroyl peroxide, di(n-propyl)peroxydicarbonate,di(sec-butyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate,di(n-propyl)peroxydicarbonate, 1,1-dimethyl-3-hydroxybutylperoxydocanoate, cumyl peroxyneoheptanoate, t-amyl peroxydecanoate,t-butyl peroxydecanoate, t-amyl peroxypivalate, t-butyl peroxypivalate,2,5-dimethyl 2,5-di(2-ethylhexanoyl peroxy) hexane, t-amylperoxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxyacetate, di-t-amyl peroxyacetate, t-butyl peroxide, di-t-amylperoxide, t-amyl perbanzoate, and t-butyl perbanzoate.

In some embodiments, the polymer precursor is a functionalized polymerhaving a backbone as described above (e.g., a polysiloxane, polyolefin,PFPE, COP, backbone or other appropriate non-polar or low-polarpolymer), or a constituent monomer or oligomer. Any unsaturatedcarbon-carbon bond may react to form higher molecular weight linearpolymers or a cross-linked network. The latter is formed when two ormore functional groups react. Examples of functional groups of thepolymer precursors include, but are not limited to, maleic anhydride,acrylics including methacrylics, acrylamides including methacrylamides,styrenics, olefins, alkenes including cyclic alkenes, alkynes, vinyls,allyls, and maleimides.

FIG. 1 provides a schematic example of formation of a cross-linkednetwork formed by radical polymerization. In FIG. 1, a radical initiator1 (solid circle) and a functionalized polymer 2 (also called a polymermatrix precursor) react to form a cross-linked network. Thefunctionalized polymer includes functional groups (hollow circle) at itsterminal ends. The organic matrix may include various signaturesindicating that it was formed in-situ by radical polymerization. Theseinclude reacted or unreacted functional groups as described above andradical initiators as described above.

An example of in-situ radical polymerization to form a solid compositematerial is provided below (see Example 1).

Step-Growth/Condensation Polymerization

In some embodiments, the in-situ polymerization is performed usingstep-growth polymerization. In some embodiments, the step-growthpolymerization occurs by condensation and may also be referred to ascondensation polymerization.

FIG. 2 provides schematic examples of formation of a linear polymer anda cross-linked polymer network by condensation polymerization. The twotypes of functional groups are labeled “A” and “B”. Examples offunctional group A include isocyanates and blocked isocyanates. Examplesof blocking agents include phenols, oximes, and secondary amines.Examples of functional group B include amines (which formpoly(urea-urethanes)), alcohols (which form polyurethanes), and thiols(which form polythiourethanes). As such, the groups formed may beurea-urethanes, urethanes, or thiourethanes.

Higher molecular weight linear polymers are formed when functionalizedpolymers of type A and type B are reacted. As also shown in FIG. 2, across-linked polymer network may be formed using multi-functionalcross-linkers.

The organic matrix may include various signatures indicating that it wasformed in-situ by condensation polymerization. These include unreactedfunctional groups as described above and formed urea-urethane, urethane,and thiourethane groups as described above.

There are several challenges to using condensation polymerization tofabricate the composite materials described herein. First, anybyproducts should not react with the inorganic phase of the composite.For example, condensation polymerization between acids or acid halogensand alcohols, amines or thiols form water and acid byproducts that mayreact with sulfide glasses. Condensation polymerization may be performedif the polymerization proceeds with no byproducts or forms onlynon-reactive byproducts.

Another challenge with condensation polymerization is that, unlikeradical polymerization, it is spontaneous. The condensationpolymerization reactions proceed with polymer precursors (i.e.,monomers, oligomers, or polymers) functionalized with two differenttypes of functional groups that react with each other. As such, forin-situ polymerization, one or both of the functional groups should beblocked. The reaction may then be initiated by unblocking thermallyreactive components.

Polyurethane polymerization reactions of isocyanates or blockedisocyanates with alcohols, amines or thiols occur without negativeeffects on sulfide glasses. According to various embodiments,polyurethanes, poly(urethane-ureas), and polythiourethanes polymers areformed through polycondensation reactions between components that may beone or more of polymerizable monomers, functional polymers and/oroligomers, and chain extenders and cross-linkers. The reaction typicallyoccurs between isocyanates or blocked isocyanates and one or more secondreactive components, such as alcohols, amines or thiols.

Examples of isocyanates include aromatic isocyanates (e.g.,diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate (PPDI),toluene diisocyanate (TDI)), aliphatic isocyanates (e.g., hexamethylenediisocyanate (HDI) and isophorone diisocyanate (IPDI)), and otherisocyanate-functionalized polymers, oligomers, and prepolymers.

Blocked isocyanates are typically formed by the reaction of anisocyanate with a compound containing an active hydrogen, including, butnot limited to alcohols, phenols, lactams (e.g., ε-caprolactam), oximes(e.g., ketoximine), hydroxylamines, pyrazoles, hydroxypyridines,triazloes, imidazolines, formate, diacetone, secondary amines (e.g.,diisopropyl amine and t-butyl benzyl amine) and methylene compounds suchas malonic esters.

Examples of chain extenders include glycols, diols, and hydroxy amines.Specific examples include ethylene glycol, propylene glycol, triethyleneglycol, tetraethylene glycol, propylene glycol, dipropylene glycol,1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol,1,6-hexanediol, 1,4-cyclohexanedimethanol, ethanolamine, diethanolamine,methyldiethanolamine, phenyldiethanolamine, 4,4′-ethylene dianiline,dimethylthiotoluenediamine, diethyl toluene diamine,4,4′-methylene-bis-2,6-diethyl aniline, and m-xylene diamine.

Examples of cross-linkers include isocyanate cross-linkers,multifunctional alcohols, amines, and hydroxy amines. Specific examplesinclude glycerol, trimethylolpropane, 1,2,6-hexanetriol,triethanolamine, tetraerythritol, andN,N,N′N″-tetrakis(2-hydroxypropyl)ethylenediamine.

In some embodiments, a mixture of components containing blockedisocyanates undergoes polymerization only at elevated temperatures, asthermal dissociation, and hence release of the blocking agent andreactive isocyanate groups, occurs.

An example of condensation polymerization to form a solid compositematerial is provided below (see Example 2).

Ring Opening Polymerization

Ring opening polymerization processes are based on the use ofnucleophiles such as amines, alcohols and thiols to ring openepoxy-terminated polymers or small molecules, and form chemical bondsand/or cross-links. For the composite materials described herein, theprocess may be limited by a catalytic effect of sulfide glass onring-opening of epoxy-terminated molecules. The catalysis may induce aspontaneous and premature polymerization. To control polymerization,blocked functional groups or functional groups having relatively lowreactivity may be employed. For example, sterically hindered epoxides,such as epoxycyclohexane, or bulkier, less reactive nucleophiles, assecondary or tertiary alcohols or secondary amines with bulkysubstituents can be used.

The ring opening polymerization reactions proceed with polymerprecursors (i.e., monomers, oligomers, or polymers) functionalized withtwo different types of functional groups that react with each other.FIG. 3 provides schematic examples of formation of a linear polymer andcross-linked polymer networks by ring-opening polymerization. The twotypes of functional groups are labeled “A” and “B”. A one-protonfunctional group A may be used to form linear polymers, with examplesincluding alcohols, secondary amines, and thiols. A two-protonfunctional group A may be used to form cross-linked networks withexamples including primary amines. Examples of functional group Binclude epoxy resins, oxiranes, glycidyl groups, and alkene oxides. Asshown, cross-linked polymer networks may also be formed with functionalcross-linkers. Examples of functional cross-linkers includemulti-functional (greater or equal to 3) small molecules, amines,alcohols, thiols, and oxiranes. The formed group is a cured epoxy resin.

In some embodiments, the in-situ polymerization is an epoxidepolymerization. Epoxy resins include epoxide-functionalized polymers,oligomers, and prepolymers, or a mixture of thereof. Theepoxy-functionalities include glycidyl, oxides of cyclic alkene (e.g.,epoxycyclohexyl), and oxiranes. Examples of epoxy prepolymers includebisphenol A, bisphenol F and novolac as well as linear and cyclicaliphatic epoxy resins, such as butanediol diglycidyl ether, hexanedioldiglycidyl ether, trimethylpropane triglycidyl ether, and3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate.

The functional epoxy resins are cured (cross-linked) through either acatalytic homopolymerization or reaction with hardeners/curatives. Thehardeners include multifunctional aliphatic, cycloaliphatic, andaromatic amines (e.g., diethylenetriamine, triethylenetetramine,tetraethylenepentamine, diproprenediamine, di ethylaminopropylamine,hexamethylenediamine, N-aminoethylpiperazine, menthane diamine,isophoronediamine, m-xylenediamine, metaphenylene diamine, anddiaminodiphenylmethane), polyamide resins, alcohols, thiols, polythiols,polysulfide resins, phenols, acids, and acid anhydrides (e.g., phthalic,trimellitic, pyromellitic, maleic, tetrahydrophthalic,methyltetrahydrophthalic, dodecenyl succinic, hexahydrophthalic, andsuccinic anhydrides). The catalytic homopolymerization of epoxy resinmay occur in presence of anionic catalysts, such as tertiary andsecondary amines (e.g., piperidine, N,N-dimethylpiperidine,benzyldimethylamine) and imidazoles (e.g., 2-methylimidazole and2-ethyl-4-methylimidazole) or in the presence of cationic catalysts,like boron trifluoride. In some embodiments, the reaction is catalyzedby lithium sulfide glass. The epoxy resins shrink during the curingprocess, with the shrinkage typically about 3-10%. Shrinkage occurs atthe gel point and increases with increasing gelation of the resin.

The organic matrix may include various signatures indicating that it wasformed in-situ by ring opening polymerization. These include unreactedfunctional groups as described above and epoxy resins.

An example of in-situ ring opening polymerization to form a solidcomposite material is provided below (see Example 4).

Polymer Binder

In some embodiments, the solid composite materials include a highmolecular weight polymer binder as part of the polymer matrix describedabove. The presence of a small amount of a polymer binder can improveprocessability, for example, turning a powdery mixture into a castablethin film. In some embodiments, a binder may be added prior toprocessing steps such as casting, extruding, or laminating the film toprovide mechanical strength to the material before the film undergoesthermally activated or ultraviolet-activated in-situ polymerization.

The polymer binder is a high molecular weight (at least 100 kg/mol)polymer. In some embodiments, the polymer binder has a non-polarbackbone. Examples of non-polar polymer binders include polymers orcopolymers including styrene, butadiene, isoprene, ethylene, andbutylene. Styrenic block copolymers including polystyrene blocks andrubber blocks may be used, with examples of rubber blocks including PBDand polyisoprene. The rubber blocks may or may be hydrogenated. Specificexamples of polymer binders are styrene ethylene butylene styrene(SEBS), styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS),styrene-butadiene rubber (SBR), PSt, PBD, polyethylene (PE), andpolyisoprene (PI).

The backbone may be the same or different than the backbone formed bythe functionalized polymers described above. The high molecular weightpolymer is not functionalized or has end groups (such as methyl endgroups) that do not interact with the inorganic phase.

If present, the amount of polymer binder in the solid composite materialmay be limited to maintain conductivity. According to variousembodiments, the polymer binder is between 0.5% and 5% by weight of thecomposite. In some embodiments, the polymer binder is between 0.5% and4% by weight of the composite, between 0.5% and 3% by weight of thecomposite, between 0.5% and 2.5% by weight of the composite, between0.5% and 2% by weight of the composite, or between 0.5% and 1.5% byweight of the composite.

If present, the polymer binder is generally not covalently bonded to thein-situ polymerized linear polymers or cross-linked polymer network.

Composite Materials

The solid-state compositions described herein generally include aninorganic solid phase and an organic polymer matrix as described above.The compositions may depend in part on the application, with exampleapplications including solid-state electrolytes and solid-stateelectrodes.

Loading refers to weight percent or volume percent that a componentoccupies in the composition or part thereof. In the description herein,loadings are provided as weight percentages. The organic matrix,including the in-situ polymerized precursor and a polymer binder (ifpresent), may fill the space between the inorganic particles such thatthere is no or minimal void space in the composition and has desirablemechanical properties. If the loading is too high, however, it canreduce conductivity. The total polymer loading in a solid-statecomposite may be between 2.5% and 60%, by weight.

According to various embodiments, the polymer matrix loading in thecomposites is relatively high, being at least 2.5%, at least 5%, atleast 10%, at least 11%, at least 12%, at least 13%, at least 14%, atleast 15%, at least 16%, at least 17%, at least 18%, at least 19%, atleast 20%, at least 22%, at least 24%, at least 26%, at least 28%, atleast 30%, at least 32%, least 40%, at least 45%, or at least 50%, ineach case by weight. The total polymer loading in the composite materialdoes not exceed 60% by weight.

According to various embodiments, the composite material may includeunreacted reactants and byproducts of the in-situ polymerizationreaction. These will depend on the reactants and type of polymerizationreaction employed, and may be used as a signature to identify if thecomposite was formed via an in-situ polymerization reaction.

In some embodiments, the solid-state compositions consist essentially ofinorganic ionically conductive particles and a polymer matrix, alongwith any unreacted reactants and byproducts of an in-situ polymerizationreactant. The polymer matrix consists essentially of the polymerizedproduct of an in-situ polymerization reaction in some embodiments. Insome embodiments, the polymer matrix consists essentially of thepolymerized product of an in-situ polymerization reaction and a highmolecular weight polymer binder.

In alternative embodiments, one or more components other than theinorganic ionically conductive particles, one or more first components,and one or more polymer binders may be added to the solid-statecompositions. According to various embodiments, the solid-statecompositions may or may not include an added salt. Salts such as lithiumsalts (e.g., LiPF₆, LiTFSI), potassium salts, and sodium salts may beadded to improve conductivity. However, in some embodiments, they arenot used with the contacting ionically conductive particles responsiblefor all of the ion conduction. In some embodiments, the solid-statecompositions include substantially no added salts. “Substantially noadded salts” means no more than a trace amount of a salt. In someembodiments, if a salt is present, it does not contribute more than 0.05mS/cm or 0.1 mS/cm to the ionic conductivity. In some embodiments, thesolid-state composition may include one or more conductivity enhancers.In some embodiments, the electrolyte may include one or more fillermaterials, including ceramic fillers such as Al₂O₃. If used, a fillermay or may not be an ion conductor depending on the particularembodiment. In some embodiments, the composite may include one or moredispersants. Further, in some embodiments, an organic phase of asolid-state composition may include one or more additional organiccomponents to facilitate manufacture of an electrolyte having mechanicalproperties desired for a particular application. In some embodiments,discussed further below, the solid-state compositions includeelectrochemically active material.

In some embodiments, the solid-state composites have a modulus of atleast about 9 GPa (about 2.5× the modulus of lithium metal) to preventthe growth of lithium dendrites when used as an solid electrolyte. Thecomposites may be microscopically dense and compliant and can beprocessed to different shapes (for example, pellets).

The solid-state composites may be characterized by having high ionicconductivity. In some embodiments, the conductivity is close to that ofthe pristine ion conductor particles, for example, and may becharacterized as a percentage of that of the pristine particles, e.g.,at least 10%, 50%, or 70% of the pristine ion-conductor particles. Thesolid-state composites may also be characterized as having ionicconductivity of at least 1.0×10⁻⁴ S/cm.

The polymers of the organic matrix may be characterized by a backbone asdescribed above. In some embodiments, the polymers may include one ormore different types of functional groups that may be attached to theterminal ends of polymer matrix precursors (e.g., for polymerization orinteraction with the inorganic phase) and/or attached along variouspoints of the backbone of a polymer matrix precursor (e.g., forcross-linking). Further, in some cases, unreacted reactants includingfunctional groups may be present in the organic phase, as part offunctionalized polymers, or functional cross-linkers or chain extenders.

Examples of functional groups include a primary amine functional group(—NH₂) a secondary amine functional group (—NRH, where R is alkyl oraryl), an alcohol functional group (—OH), a thiol functional group(—SH), an isocyanate functional group (—N═C═O), an alkenyl functionalgroup (—RC═CR₂, where each R is individually H, alkyl, or aryl), analkynyl functional group (—C≡CR, where R is H, alkyl, or aryl), a vinylfunctional group (—CH═CH₂), and an allyl functional group (—CH₂—CH═CH₂).The attachment point to the backbone is indicated by “—”.

Further examples include a (meth)acrylate functional group,(meth)acrylamide functional group, a styrenic functional group, and amaleimide functional group as shown below, where R is H, alkyl, or aryland

indicates the attachment point to the backbone.

Once reacted, the above functional groups may form linking groups (alsoreferred to as linkers) in an in-situ polymerized matrix. As such, anin-situ polymerized matrix may be characterized by the presence of oneor more of the following:—CH₂CH(H/CH₃)(R) where R═—C(O)—O—,—C(O)—NR—,—C₆H₄—, or  1)

—NH—C(O)—NR—, where R is H,alkyl or aryl;  2)—NH—C(O)—O—; and  3)—NH—C(O)—S—.  4)These linking groups may attached to a backbone or all or part of achain extending or cross-linking group.

The polymer matrix may be characterized as the product of the in-situpolymerization reaction or reactions used to form it as described above.For example, a poly(urethane) may be formed by reaction of an isocyanatewith an alcohol. In some embodiments, the polymer matrix includes apoly(urethane), a poly(ureaurethane), poly(thiourethane), apoly(acrylate), a poly(methacrylate), a poly(maleimide),poly(acrylanmide), a poly(methacrylamide), a polyolefin, or apolystyrene. FIG. 14 provides examples of these polymers in an in-situpolymerized polymer matrix.

Processing

The solid-state compositions may be prepared by any appropriate methodwith example procedures described below with reference to theExperimental results. Uniform films can be prepared by solutionprocessing methods. In one example method, all components are mixedtogether by using various laboratory and industrial equipment such assonicators, homogenizers, high-speed mixers, rotary mills, verticalmills, and planetary ball mills. Mixing media can be added to aidhomogenization, by improving mixing, breaking up agglomerates andaggregates, thereby eliminating film imperfection such as pin-holes andhigh surface roughness. The resulting mixture is in a form of uniformlymixed slurry with a viscosity varying based on the hybrid compositionand solvent content. The substrate for casting can have differentthicknesses and compositions. Examples include aluminum, copper andmylar. The casting of the slurry on a selected substrate can be achievedby different industrial methods. In some embodiments, porosity can bereduced by mechanical densification of films (resulting in, for example,up to about 50% thickness change) by methods such as calendaring betweenrollers, vertical flat pressing, or isostatic pressing. The pressureinvolved in densification process forces particles to maintain a closeinter-particle contact. External pressure, e.g., on the order of 1 MPato 300 MPa, or 1 MPa to 100 MPa, is applied. In some embodiments,pressures as exerted by a calendar roll are used. The pressure issufficient to create particle-to-particle contact, though kept lowenough to avoid uncured polymer from squeezing out of the press.Polymerization, which may include cross-linking, may occur underpressure to form the matrix. In some implementations, athermal-initiated or photo-initiated polymerization technique is used inwhich application of thermal energy or ultraviolet light is used toinitiate polymerization. The ionically conductive inorganic particlesare trapped in the matrix and stay in close contact on release ofexternal pressure. The composite prepared by either of the above methods(pellets or thin films) is incorporated to an actual solid-state lithiumbattery by well-established methods.

In some embodiments, the films are dry-processed rather than processedin solution. For example, the films may be extruded. Extrusion or otherdry processing may be alternatives to solution processing especially athigher loadings of the organic phase (e.g., in embodiments in which theorganic phase is at least 30 wt %).

FIG. 4a provides an example of a schematic depiction of a cast filmincluding ionically conductive inorganic particles in a polymer matrixundergoing in-situ polymerization to cross-link the polymer chains underapplied pressure. In the example of FIG. 4, the cast film is subject toan applied pressure that densifies the film and forces the ionicallyconductive particles into close contact. An external stimulus is appliedto initiate polymerization, which in the example of FIG. 4, cross-linkspolymer chains of the polymer matrix to form a polymer network. Thepressure is released, with the cross-linked film remaining dense withthe ionically conductive particles into close contact. In alternateembodiments, the organic matrix includes polymers without anycross-linking. Further, as indicated above, in some embodiments, thefilm is not cast.

FIG. 4b provides an example of a schematic depiction of a cast filmincluding ionically conductive inorganic particles in a polymer matrixundergoing in-situ polymerization according to certain embodiments ofthe invention to cross-link the polymer chains without applied pressure.In these embodiments, the film undergoes sufficient contraction due tothe in-situ polymerization itself that particle-to-particle contact andincrease in ionic conductivity occurs. The level of contraction for aparticle polymerization depends on several factors, including the typeof polymerization, the volume of organic matrix in the composite, andthe type and number of polymerizable groups in the pre-polymerizedcomposites. With respect to type of polymerization, step-growthpolymerization undergoes more volume change than chain-growthpolymerization, which undergoes more volume change than ring openingpolymerization. For the cross-linked systems described above, thelargest contraction would result from step-growth polymerization such aspolyurethane polymerization with blocked isocyanates, followed by achain-growth polymerization such as radical polymerization (e.g., PBDcross-linking, PFPE or PDMS diacrylate crosslinking), followed byring-opening polymerization such as an epoxy-cured matrix. Higherorganic matrix volume percentages and lower inorganic particle volumepercentages also lead to more contraction. Finally, the more functionalgroups that are converted during polymerization, the more the film willcontract.

In some embodiments, dual-cure methods are provided. In such methods,two reactants that polymerize at different temperatures are provided.For example, in a step-growth polymerization a monomer that forms onlyhigher molecular weight linear polymers (i.e., a difunctional or N=2monomer) may polymerize at 100° C., and a functional cross-linker thathas three functional groups (N=3) may polymerize at 180° C. The polymerformed with N=2 monomer may be a thermoplastic, and can be re-shapedunder temperature and pressure, whereas the N=3 functional cross-linkermay a thermoset that cannot be re-shaped. Thus, a first in-situprocessing operation at 100° C. may be performed to hold the compositetogether with a subsequent in-situ processing operation performed at180° C. to cross-link the composite in its final form. The first curecan provide mechanical strength to the material before the filmundergoes thermally activated or ultraviolet-activated in-situpolymerization in some embodiments. An example of a dual cure systemincluding a difunctional monomer (isophoronediisocyanate-diisopropylamine (IPDI-DIPA)) and blocked trifunctionalisocyanate (poly[(phenyl isocyanate)-co-formaldehyde] PPFI-DIPA) forin-situ polyurethane formation is described is provided below in Example9.

In some embodiments, a higher molecular weight thermoplastic polymer canbe pre-polymerized ex-situ and then mixed with the ionically conductiveparticles. This may be done instead of polymerizing N=2 monomersin-situ, for example. The higher molecular weight thermoplastic may beprepared by reacting a backbone polymer with isocyanate as describedabove.

Electrolytes

In one aspect of the invention, solid-state composite electrolytes areprovided. The solid-state composite electrolytes may be any of thesolid-state composite material described above. The electrolyte may beformed directly on a functional substrate, such as an electrode, orformed on a removable substrate that is removed before assembling thesolid-state electrolyte to other components of a battery.

In some embodiments, solid-state composite electrolytes consistingessentially of a polymer matrix and the ionically conductive inorganicparticles, along with any unreacted reactant or byproduct, as describedabove are provided. However, there may be other components of theelectrolytes as described above. In some such embodiments, thepolymerized precursor, the high molecular weight polymer binder (ifpresent), ionically conductive inorganic particles, and any unreactedreactant or byproduct (if present) constitute at least 90% by weight ofthe solid-state composite electrolyte, and, in some embodiments, atleast 95% by weight of the solid-state composite electrolyte.

In some embodiments, ionically conductive amorphous inorganic particlesconstitutes at least 60% by weight of the solid-state electrolyte. Insome such embodiments, the balance of the solid-state electrolyte is thepolymer matrix and any unreacted reactant and byproduct. In someembodiments, ionically conductive amorphous inorganic particlesconstitutes at least 80% by weight of the solid-state electrolyte. Insome such embodiments, the balance of the solid-state electrolyte is thepolymer matrix and any unreacted reactant and byproduct. In someembodiments, ionically conductive amorphous inorganic particlesconstitutes at least 85% by weight of the solid-state electrolyte. Insome such embodiments, the balance of the solid-state electrolyte is thepolymer matrix and any unreacted reactant and byproduct.

Other components can include alkali metal ion salts, including lithiumion salts, sodium ion salts, and potassium ion salts. Examples includeLiPF₆, LiTFSI, LiBETI, etc. However, in some embodiments, thesolid-state electrolytes are substantially free of alkali metal ionsalts.

In some embodiments, the electrolyte may include an electrodestabilizing agent that can be used to form a passivation layer on thesurface of an electrode. Examples of electrode stabilizing agents aredescribed in U.S. Pat. No. 9,093,722. In some embodiments, theelectrolyte may include conductivity enhancers, fillers, or organiccomponents as described above.

The composite solid-state electrolytes may be used in any solid-statealkali-ion or alkali-metal battery, including lithium-ion batteries,sodium-ion batteries, lithium-metal batteries, and sodium-metalbatteries. The composite solid-state electrolytes are well-suited forbatteries in which dendrite growth is a concern. For example, in someembodiments, an electrolyte for a lithium metal battery is provided. Thecomposite solid-state electrolytes enable the use of lithium metalanodes by resisting dendrites. The composite solid-state electrolytesmay be used with any cathode material, including sulfur cathodes. Theorganic phase components described above do not dissolve polysulfidesand are suited for use with lithium-sulfur batteries.

A solid film electrolyte composition of the present invention may be ofany suitable thickness depending upon the particular battery design. Formany applications, the thickness may be between 10 microns and 250microns, for example 100 microns. In some embodiments, the electrolytemay be significantly thicker, e.g., on the order of millimeters.

Example loadings for solid-state composite electrodes according toembodiments of the present invention are given below in Table 1.

TABLE 1 Example Loadings for Solid-State Composite Electrolytes % Weightof Examples Total Inorganic phase Inorganic Sulfide glass  40%-97.5%ionically 40%-90% conductive 65%-90% particles % Weight of Examplesorganic phase Organic Phase Polymerized HLBH, LBH, 50%-99% 2.5%-60% precursor PDMS 80%-99% 10%-60% 95%-99% 10%-35% High molecular SEBS, SBS, 1%-50% weight polymer SIS, SBR, 100  1%-20% binder kg/mol and 1%-5%above, and mixtures thereof

Table 1 provides loadings for compositions for which the organic matrixincludes a high molecular weight polymer binder. The loadings do notconsider unreacted reactants or byproducts—that is, unreacted reactantsor byproducts, which may be present in trace or greater amounts, are notincluded in the loadings. For compositions that do not include a highmolecular weight polymer binder, the high end of each example range forthe polymerized precursor (99%) is replaced by 100%, with the low end ofeach example range for the binder (1%) replaced by 0.

Electrodes

In one aspect of the invention, electrodes including the solid-statecomposites are provided. The solid-state composites further include anelectrode active material, and optionally, a conductive additive. Inembodiments in which a high molecular weight binder is present, the highmolecular weight polymer binder may constitute between 1% and 50% byweight of the organic phase, with the polymerized precursor constitutingat least 50% by weight of the organic phase. The organic phase consistsessentially of an in-situ polymerized precursor, an optional highmolecular weight polymer binder, and any unreacted reactant andbyproduct that may be present according to some embodiments. In otherembodiments, it may include one or more additional components asdescribed above. Example loadings of embodiments of the presentinvention are given below in Table 2.

TABLE 2 Example Loadings for Solid-State Composite Electrodes % Weightof % Weight of Examples powder Total Inorganic phase - Active Li₂S, LCO,30-80% 85-97% electrode powder Material NCA, graphite, 30-50% silicon,sulfur Conductive Activated  5-25% Additive carbon 10-20% InorganicSulfide glass 15-60% ionically 30-50% conductive particles % Weight ofExamples organic phase Organic Phase Polymerized HLBH, LBH, 50%-99%3-15% precursor PDMS 80%-99% 95%-99% High molecular SEBS, SBS,    1-50%weight polymer SIS, SBR, 100  1%-20% binder kg/mol and 1%-5% above, andmixtures thereof

Table 2 provides loadings for compositions for which the organic matrixincludes a high molecular weight polymer binder. Unreacted reactants orbyproducts, which may be present in trace or greater amounts, are notincluded in the loadings. For compositions that do not include a highmolecular weight polymer binder, the high end of each example range forthe polymerized precursor (99%) is replaced by 100%, with the low end ofeach example range for the binder (1%) replaced by 0.

In some embodiments, the solid-state electrodes are cathodes includingan in-situ polymerized polymer matrix, inorganic ionically conductiveparticles, and an active material. In some embodiments, the solid-stateelectrodes are anodes including an in-situ polymerized polymer matrix,inorganic ionically conductive particles, and an active material.

Example cathode active materials include lithium cobalt oxide (LCO),lithium manganese oxide (LMO), lithium nickel cobalt aluminum oxide(NCA), lithium iron phosphate (LFP), and lithium nickel cobalt manganeseoxide (NCM). Example anode active materials include graphite and othercarbon-containing materials, silicon and silicon-containing materials,tin and tin-containing materials, lithium and lithium alloyed metals.

In some embodiments, the solid-state electrodes are sulfur cathodesincluding an in-situ polymerized polymer matrix, inorganic ionicallyconductive particles, and sulfur-containing active material. In someembodiments, the composite solid-state cathodes are incorporated intolithium-sulfur batteries with the composite solid-state cathodesincluding a an in-situ polymerized polymer matrix, an optional highmolecular weight polymer binder, inorganic ionically conductiveparticles, lithium sulfide (Li₂S) particles, and a carbon conductivematerial.

According to various embodiments, the solid-state electrodes are thinfilms having thicknesses of less than 200 microns, and in someembodiments, less than 100 microns. The areal capacity may be between 1mAh/cm² and 10 mAh/cm² n some embodiments.

In one aspect of the invention, electrode/electrolyte bilayers thatinclude the solid-state composite compositions are provided. Thebilayers include a solid-state composite electrode and a solid-statecomposite electrolyte as described above. Each of the ionicallyconductive inorganic particles, the in-situ polymerized polymer matrix,and the high molecular weight polymer binder (if present) may beindependently selected for the electrode and the electrolyte, such thateach component of the electrode may be the same or different as that inthe electrolyte. The solid-state electrodes are thin films havingthicknesses of less than about 200 microns, and in some embodiments,less than about 100 microns. The solid-state electrolyte, which contactsthe solid-state electrode, may have a thickness of less than about 200microns. In some embodiments, it is between 5 microns and 50 micronsthick, e.g., between 25 microns and 50 microns thick.

Battery

Provided herein are alkali metal batteries and alkali metal ionbatteries that include an anode, a cathode, and a compliant solidelectrolyte composition as described above operatively associated withthe anode and cathode. The batteries may include a separator forphysically separating the anode and cathode.

Examples of suitable anodes include but are not limited to anodes formedof lithium metal, lithium alloys, sodium metal, sodium alloys,carbonaceous materials such as graphite, and combinations thereof.Examples of suitable cathodes include, but are not limited to cathodesformed of transition metal oxides, doped transition metal oxides, metalphosphates, metal sulfides, lithium iron phosphate, sulfur andcombinations thereof. In some embodiments, the cathode may be a sulfurcathode. Additional examples of cathodes include but are not limited tothose described in Zhang et al., US Pat. App. Pub No. 2012/0082903, atparagraph 178, which is incorporated by reference herein. In someembodiments, an electrode such as a cathode can contain a liquid, suchas described in Y. Lu et al., J. Am. Chem. Soc. 133, 5756-5759 (2011),incorporated by reference herein.

In an alkali metal-air battery such as a lithium-air battery, sodium-airbattery, or potassium-air battery, the cathode may be permeable tooxygen (e.g., mesoporous carbon, porous aluminum, etc.), and the cathodemay optionally contain a metal catalyst (e.g., manganese, cobalt,ruthenium, platinum, or silver catalysts, or combinations thereof)incorporated therein to enhance the reduction reactions occurring withlithium ion and oxygen at the cathode.

In some embodiments, lithium-sulfur cells are provided, includinglithium metal anodes and sulfur-containing cathodes. As noted above, thesolid-state composite electrolytes described herein uniquely enable botha lithium metal anode, by preventing dendrite formation, and sulfurcathodes, by not dissolving polysulfide intermediates Li₂S_(n) that areformed at the cathode during discharge.

A separator formed from any suitable material permeable to ionic flowcan also be included to keep the anode and cathode from directlyelectrically contacting one another. However, as the electrolytecompositions described herein are solid compositions, they can serve asseparators, particularly when they are in the form of a film.

As described above, in some embodiments, the solid compositecompositions may be incorporated into an electrode of a battery. Theelectrolyte may be a compliant solid electrolyte as described above orany other appropriate electrolyte, including liquid electrolyte.

In some embodiments, a battery includes an electrode/electrolytebilayer, with each layer incorporating the ionically conductivesolid-state composite materials described herein.

FIG. 15 shows an example of a schematic of a cell 100 according tocertain embodiments of the invention. The cell 100 includes a negativecurrent collector 102, an anode 104, an electrolyte 106, a cathode 108,and a positive current collector 110. The negative current collector 102and the positive current collector 110 may be any appropriateelectronically conductive material, such as copper, steel, gold,platinum, aluminum, and nickel. In some embodiments, the negativecurrent collector 102 is copper and the positive current collector 110is aluminum. The current collectors may be in any appropriate form, suchas a sheet, foil, a mesh, or a foam. According to various embodiments,one or more of the anode 104, the cathode 108, and the electrolyte 106is a solid-state composite including a first component as describedabove. In some embodiments, each of the anode 104, the cathode 108, andthe electrolyte 106 is two- or three-component solid-state composite, asdescribed above. FIG. 16 shows an example of schematic of a lithiummetal cell as-assembled 200 according to certain embodiments of theinvention. The cell as-assembled 200 includes a negative currentcollector 102, an electrolyte 106, a cathode 108, and a positive currentcollector 110. Lithium metal is generated on first charge and plates onthe negative current collector 102 to form the anode. One or both of theelectrolyte 106 and the cathode 108 may be a composite material asdescribed above. In some embodiments, the cathode 108 and theelectrolyte 106 together form an electrode/electrolyte bilayer asdescribed above. FIG. 17 shows an example of a schematic of a cell 100according to certain embodiments of the invention. The cell 100 includesa negative current collector 102, an anode 104, a cathode/electrolytebilayer 112, and a positive current collector 110.

All components of the battery can be included in or packaged in asuitable rigid or flexible container with external leads or contacts forestablishing an electrical connection to the anode and cathode, inaccordance with known techniques.

EXAMPLE EMBODIMENTS Example 1: Radical Polymerization PFPE with ThermalInitiator

In a glovebox operating under argon atmosphere, 2.4 g of lithium sulfideglass (Li₂S:P₂S₅=75:25) was placed in a cup. 1.04 g of PFPEdimethacrylate (Fluorolink MD 700, Solvay) was added, followed by 0.051g of benzoyl peroxide and 7.3 g of dry Fluorinert 70. The cup was placedin a Thinky mixer (Thinky ARV-50LED) and mixed at 1500 rpm for 40 mins.The slurry was cast on aluminum foil using a doctor blade. The film wasdried on the coater, while maintaining the vacuum, then was transferredto an antechamber and dried under vacuum at 60° C. The dried film wasscraped off and the material was pressed into pellets under 120 MPa,using hydraulic press, and then heated at 125° C. for two hours. Afterthat, the heating was removed, the pellet was cooled to room temperatureand only then the pressure was released.

Example 2 Part 1: Synthesis of Diisopropylamine-Blocked4,4-Diisocyanatodiphenylmethane (MDI-DIPA)

10.0 g of 4,4-diisocyanatodiphenylmethane (MDI) was weight out in aglovebox and placed in a dry 250 mL Schlenk flask equipped with a stirbar, followed by the addition of 180 mL of anhydrous toluene. The flaskwas closed with a rubber septum and placed on a stir plate undernitrogen flow. Next 11.2 mL of dry diisopropylamine (DIPA) was slowlyadded to the mixture over 5 mins. As the mixture progresses a phaseseparation of the product from the solution was observed. The mixturewas stirred at room temperature for three hours, then the bottom phaseof the mixture was separated and residual solvent was removed undervacuum resulting in a white solid. The product was further dried undervacuum at 60° C. for 24 hrs.

Example 2 Part 2: Step-Growth/Condensation Polymerization HydrogenatedPolybutadiene Diol with Blocked Diisocyanate

In a glovebox operating under argon atmosphere, 2.55 g of lithiumsulfide glass (Li₂S:P₂S₅=75:25) was placed in cup, next, 0.37 g ofhydrogenated polybutadiene diol (Krasol HLBH-P 2000, Cray Valley) and0.080 g of MDI-DIPA were added as a 25 wt. % solution in1,2,4-trimethylbenzene, and extra 0.3 g of 1,2,4-trimethylbenzene wasplaced in the cup. The cup was placed in a Thinky mixer (ThinkyARV-50LED) and mixed at 1500 rpm. The slurry was cast on aluminum foilusing a doctor blade. The film was dried on the coater, whilemaintaining the vacuum, then was transferred to an antechamber and driedunder vacuum without heat for 16 hrs.

The dry film was cut into three 50×70 mm rectangles, each post-processedin a different way. All pieces of film were subjected to a pressure of15 MPa for two hours using a vertical laminating press, however each wasexposed to different temperatures while under pressure. Theconductivities of films were measured in as Al|Al symmetrical cellssealed pouches. Each sample was measured at three different appliedpressures at room temperature. Table 3 below shows the results:

TABLE 3 Conductivity for composite films processed at differenttemperatures Cond./S · cm⁻¹ Sample Press Applied Force/MPa # Temp./° C.0.1 15 95* 1 25 1.4 · 10⁻⁶ 6.6 · 10⁻⁶ 6.7 · 10⁻⁵ 2 1.7 · 10⁻⁶ 1.7 · 10⁻⁵6.6 · 10⁻⁵ 3 100 — 9.4 · 10⁻⁵ 1.2 · 10⁻⁴ 4 — 8.3 · 10⁻⁵ 1.0 · 10⁻⁴ 5 1409.5 · 10⁻⁵ 1.1 · 10⁻⁴ 1.0 · 10⁻⁴ 6 1.1 · 10⁻⁴ 1.2 · 10⁻⁴ 1.1 · 10⁻⁴*Values after thickness adjustment due to densification.

The temperature for the reaction to occur was determined by differentialscanning calorimetry (DSC). DSC analysis of cast, dry sample (exothermof reaction). The cross-linking was confirmed by DSC andthermogravimetric analysis (TGA), by disappearance of the exothermicsignal of polymerization reaction and decreased weight loss of thesample respectively.

Referring to the above table, samples 1-4 show increased conductivitywith increased applied pressure, while samples 5 and 6 maintainconductivity even at ambient pressure (0.1 MPa). This indicates that at140° C., sufficient external energy is applied to initiate in-situpolymerization and that the in-situ polymerization allows the samples tomaintain conductivity even after pressure is released.

Example 3: Analysis of Hybrid Synthesis Via In-Situ PolyurethaneFormation

Hybrids of lithium sulfide glasses with polyurethane polymer matrix aresynthesized as described in Example 2. The formation of polyurethaneoccurs at elevated temperature between diol (polymer or small molecule)and an ‘in-situ’ generated isocyanate. The isocyanate is produced as aresult of dissociation of the blocking agent from protected isocyanate;hence, the reaction temperature has to be no lower than the temperatureof the dissociation of the blocking agent(T_(reaction)≥T_(dissociation)).

Two main analytical techniques are employed in assessment of thedecomposition process of blocked isocyanates: DSC and TGA. FIG. 5 showsa DSC thermogram of 4,4-diisocyanatodiphenylmethane blocked withdiisopropylamine (MDI-DIPA), showing two endotherms with respectiveonset temperatures of T_(1diss)=143° C. and T_(2diss)=184° C.

The presence of two endotherms on the DSC thermogram indicates that thedissociation of diisopropylamine follows a two-step process (Scheme 1).When heated to T_(diss1), only one of the isocyanate groups is unblocked(Step I, Scheme 1), and the system requires a higher temperature(≥T_(diss2)) to release the other one (Step II, Scheme 1).

The step-wise dissociation mechanism is further confirmed by TGAanalysis of MDI-DIPA, performed under isothermal conditions, at 140° C.(FIG. 6). As expected, the analysis showed a 25 wt. % loss, whichcorresponds to the loss of one DIPA molecule and correlates well withthe theoretical value of about 23 wt. %

Next, DSC was used to analyze a mixture of polymerizable componentsMDI-DIPA and HLBH2000. The data shows that in the presence of the diol(HLBH2000) the endotherm with onset temperature at T_(diss1)˜140° C.(solid line, FIG. 7) disappears, and is replaced with an endothermicpeak at T_(end1)˜136° C. (dashed line, FIG. 7). The appearance of theexotherm is an indication of the polymerization (polyurethane formation)between (blocked) isocyanate and diol. However, the disappearance of theendotherm suggests that the process occurs via one-steptransesterification, rather than two-step dissociation-condensationreaction.

Finally, DSC and TGA analyses were performed on the full hybridformulation of lithium sulfide glass and pre-matrix components,specifically HLBH2000 and MDI-DIPA, prepared by a thin-film castingmethod. The analyses provide several different pieces of information: a)temperature required to initiate ‘in-situ’ polymerization inpolyurethane hybrids (DSC), b) thermal stability of the sulfide glass inthe pre- and post-polymerized hybrid, and c) occurrence and progress ofthe polymerization in the organic matrix. FIG. 8 shows DSC traces ofpure Li₂S:P₂S₅=75:25 glass (upper trace) and the hybrid mixture of thesame sulfide glass, HLBH2000 and MDI-DIPA, before heat treatment (lowertrace). The pure glass analysis shows only one endotherm atT_(1cryst)=230° C., which is related to the glass crystallization (solidblue, FIG. 4). When the same glass is combined with the matrixcomponents, HLBH2000 and MDI-DIPA, two endothermal peaks are observedinstead. The first, smaller signal at T_(end2)˜96° C. is ascribed to thepolymerization reaction, whereas the higher intensity peak atT_(cryst2)˜162° C. corresponds to the glass crystallization. It isevident that the thermal stability of the sulfide glass decreasessignificantly in the presence of matrix components. This evidence issupported by the 67° C. drop in the crystallization temperature, andhence decreased thermal stability, of the glass in the pre-polymerizedhybrid as compared to the pure glass. On the other hand, the presence ofthe sulfide glass catalyzes the polyurethane formation reaction, whichis indicated by the shift of the polymerization endotherm fromT_(end1)˜136° C. (dashed line, FIG. 7) to T_(end2)˜96° C. (lower trace,FIG. 8).

After determining the thermal stability of the glass and thepolymerization temperature in the pre-polymerized hybrid, the thin filmis subjected to thermal post-processing. The thin film is pressed in ahorizontal lamination press at 15 MPa, then heated at 100° C. or 140° C.for 2 hrs, and cooled to room temperature, while applying the pressure.FIG. 9 shows DSC traces of the glass hybrid film treated at 100° C. and140° C. As expected, the polymerization exotherm present in thepre-polymerized hybrid (short dash, labeled ‘B’) disappears when thefilm is exposed to either 100° C. (dash-dot trace, labeled ‘A’) or 140°C. (long dash trace, labeled ‘C’), which confirms that thepolymerization reaction within the hybrid is accomplished. In addition,based on the differences in observed crystallization temperatures,significant changes in the glass stability are noticed. The glassstability decreases by 67° C. when pre-polymerized matrix is introduced,but increases in the thermally treated (polymerized) hybrid. When thehybrid is pressed at 100° C., the thermal stability of glass is only 40°C. lower (dash-dot trace, labeled ‘A’) and it fully recovers whentreated at 140° C. (long dash trace, labeled ‘C’); hence providingevidence of the glass stabilization by in-situ polyurethane formationwithin the hybrid.

TGA is used to provide additional indication that the polymerizationreaction occurred. See FIG. 10. Four samples: pure sulfide glass(labeled ‘D’), the non-treated thin film (labeled ‘B’), and the filmheated at 100° C. (labeled ‘A’) and 140° C. (labeled ‘C’), are analyzedby isothermal TGA, at 100° C. for 100 mins. The pure glass (D) is stableand shows no weight loss at 100° C. The non-treated hybrid (loses ˜1.34%of its weight which closely correlates with the theoretical value of1.25 wt. %. This number assumes a complete dissociation of alldiisopropylamine molecules from MDI-DIPA. When treated at 100° C. and140° C., that weight loss changes to 0.31% and 0.24% respectively,indicating on the polymerization reaction and DIPA evaporating from thesystem. The values of weight loss, however, may suggest limitedun-blocking efficiencies (75% and 82%) of MDI-DIPA, uncompleteevaporation of free diisopropylamine or insufficient fraction of alcoholgroups in the pre-polymerized matrix.

Example 4: Ring Opening Polymerization—PDMS Polymers with Epoxy andAmino Functional Groups

In a glovebox operating under argon atmosphere, 1.7 g of lithium sulfideglass (Li₂S:P₂S₅=75:25) was placed in a cup, next, 0.104 g of dryaminopropyl terminated polydimethylsiloxane (DMS-A11, Gelest) was added,followed by 1.0 g of dry 1,2,4-trimethylbenzene. The cup was placed in aThinky mixer (Thinky ARV-50LED) and mixed at 1500 rpm for 30 mins. Afterthat, the cup was opened and 0.196 g of dry epoxypropyl terminatedpolydimethylsiloxane (Sigma Aldrich) was added; the mixing was continuedfor 2 mins at 1500 rpm. The slurry was cast on aluminum foil using adoctor blade. The film was dried on the coater, while maintaining thevacuum, then transferred to an antechamber and dried under vacuum atroom temperature. The film was dried for 16 hrs and then calendaredusing a vertical rolling press. The film thickness changed from 97 μm to67 μm. The conductivity of the film pressed between two metal plates at24 kPSI was 2·10⁻⁵ S/cm.

Example 5: Cross-Linking of Butadiene Rubber as a Function of GlassContent

An example of a synthesis cross-linked polybutadiene sulfide glasscomposite material is shown below (Scheme 4)

The above synthesis was used to form composite films of varying weightsof glass (Li₂S:P₂S₅)=75:25, PBD (LBH-P 3000), and benzoyl peroxide (BPO)by radical cross-linking. Details of synthesizing and characterizing onesample (PDB 5) are provided in Example 6.

Film densities (before and after crosslinking) and conductivities (noexternal pressure and with external pressure) of PBD-5 andsimilarly-formed composites of various weight contents ofLi₂S:P₂S₅=75:25 glass, LBH-P 3000 and BPO are provided below in Table 4.A “-” indicates that conductivity could not be measured.

TABLE 4 Densities and conductivities of composite films before and aftercross-linking 10⁻⁴ cond./ Glass Polymer BPO % theoretical mS cm⁻¹ Samplevol. (wt.) % vol. (wt.)% vol. (wt.) % Processing density 0 in-lbs 60in-lbs PBD-1 26 (42) 72 (55) 2 (3) Dried 105% — — PBD-2 35 (53) 63 (45)2 (2) 102% — — PBD-3 45 (63) 53 (35) 2 (2) 103% — — PBD-4 47 (65) 50(33) 2 (2) 104% — — PBD-5 55 (72) 44 (27) 2 (1) Dried  84% — — PDB-5.1X-linked 102% 0.27 0.42 PBD-6 64 (79) 34 (20) 1 (1) Dried  74% — —PDB-6.1 X-linked 108% 0.61 0.58 PBD-7 72 (84) 27 (15) 1 (1) Dried  68% —— PDB-7.1 X-linked 102% 1.07 1.04 PBD-8 77 (88) 22 (12) 1 (1) Dried  62%— — PBD-8.1 X-linked  84% 1.04 1.08 PBD-9 85 (92) 14.5 (7.5)  0.5 (0.5)Dried  60% — — PBD-9.1 X-linked  77% 1.08 0.97

Theoretical density is determined from the known densities and weightpercentages of each component. Samples PBD-1 through PBD-4 were fullydensified on casting and so were not cross-linked.

FIG. 11 is a plot showing film density and conductivity vs. glass volumepercentage. Theoretical density, green density, and pressed density areshown for all samples. Conductivity at 0 in-lbs external appliedpressure and 60 in-lbs external applied pressure is shown. The compositeis as conductive without external pressure applied as with pressureapplied, suggesting that the particles of the inorganic phase are heldin place by the cross-linked network. Density is increased, includingabove the theoretical density at some loadings, after pressing.

Example 6: Radical Cross-Linking of PBD Composite Sample

Sample PBD-5 was formed and characterized by radical cross-linking asfollows. In a glovebox operating under argon atmosphere, a 15 mLpolypropylene cup was filled with 2.145 g of lithium sulfide glass(Li2S:P2S575:25) sieved to <25 μm, 0.810 g of LBH-P 3000 (LBH-P3000Krasol, Cray Valley), 0.045 g of benzoyl peroxide and 2.0 g of dry1,2,4-trimethylbenzene. Next, 25 g of Ø=10 mm zirconia balls were addedto the mixture to aid mixing; the lid was tightly secured on the cup andwrapped with an electrical tape. The cup was placed on a tube roller at80 rpm, and the slurry was mixed for 48 hrs. Next, the mixture wascoated on aluminum foil using a square applicator with 6 mil gap size,the solvent evaporated under ambient conditions and then the film wasfurther dried in an antechamber under vacuum at room temperature for 16hrs. Afterwards, a 50 mm×70 mm piece of the film was cut out, placedbetween two sheets of aluminum foil and pressed at 100° C. for 3 hrs,under 16.8 MPa using a hydraulic press. The x-linked film was cooleddown to room temperature, and only then the pressure was released. Thefilm density was measured before and after crosslinking. The filmconductivity was measured at no external pressure applied and at 60in-lbs torque force.

Example 7: In-Situ Polyurethane Synthesis

An example of a synthesis of a linear polyurethane sulfide glasscomposite according to an embodiment is shown below in Scheme 5A.

In a glovebox operating under argon atmosphere, a 30 mL Thinky cup wasfilled with 2.550 g of lithium sulfide glass (Li₂S:P₂S₅=75:25) sieved to<25 μm. A 25 wt. % solution of HLBH2000 mixed with PPFI-DIPA andIPDI-DIPA (1:9=n:n, NCO) in 1:1 molar ratio was prepared in1,2,4-trimethylbenzene and dried over molecular sieves before use. Next,1.80 g of dried stock solution was added to the glass, followed by 6 Ø=5mm zirconia balls and 0.25 g of 1,2,4-trimethylebenzene. The cup wasplaced in a Thinky mixer (Thinky ARV-50LED) and mixed at 1500 rpm for 40mins. Next, the mixture was coated on aluminum foil using a squareapplicator with 8 mil gap size, the solvent evaporated under ambientconditions and then the film was further dried in an antechamber undervacuum at room temperature for 16 hrs. Afterwards, a 50 mm×70 mm pieceof the film was cut out, placed between two sheets of aluminum foil andpressed at 140° C. for 2 hrs, under 16.8 MPa using a hydraulic press.The cross-linked film was cooled down to room temperature, and only thenthe pressure was released.

Example 8: Polyurethane Crosslinking as a Function of Glass Content

Polyurethane composite films of different polymer compositions wereprepared and characterized as described in Example 7. The results areshown in Table 5, below.

TABLE 5 Poly Glass Polymer 10⁻⁴ cond./S cm⁻¹ Sample wt. % compositionProcessing 0 in-lbs 60 in-lbs PU-1.1 62.5 HLBH2000, 100° C., 48 hrs~0.001 ~0.003 PU-2.1 70 IPDI- 140° C., 2 h, 1.25 1.14 PU-4.1 85DIPA:PPFI- 6 tons 1.97 2.22 DIPA (9:1, n/n) PU-5 85 HLBH2000, Dried 0.020.67 PU-5.1 MDI-DIPA 140° C., 2 h, 1.03 1.12 6 tons

Example 9: Dual Cure Polymerization

Isophorone diisocyanate-diisopropylamine (IPDI-DIPA) is a blockeddiisocyanate that acts as a difunctional monomer in polyurethaneformation and can only participate in formation of higher molecularweight, linear polymers. A DSC trace of IPDI-DIPA (not shown) indicatesa presence of two endotherms, at about 75° C. and 100° C., and confirmsa step-wise decomposition of blocked diisocyanate (Scheme 6A) with arelease of two diisopropylamine molecules per IPDI-DIPA.

Poly[(phenyl isocyanate)-co-formaldehyde] (PPFI-DIPA) is a blockedtrifunctional isocyanate, that acts as a cross-linker during in-situpolyurethane formation, and is responsible for the formation of apolymer network. A DSC trace of PPFI-DIPA (not shown) shows a presenceof three endotherms, at about 140° C., 165° C., and 190° C. The peakscorrespond to a consecutive loss of three diisopropylamine molecules perone PPFI-DIPA, and confirms a step-wise decomposition of blockedcross-linker (Scheme 6B).

FIG. 12 shows DSC traces of pure Li₂S:P₂S₅=75:25 sulfide glass (dashdot) and a composite formed from the sulfide glass, IPDI-DIPA, PPFI-DIPAbefore (solid) and after) in-situ polymerization of a polyruethanematrix of the composite. In all cases, the exothermic peak related toglass crystalization appears at about 245-250° C., which indicates avery good resistance of glass to crystallization in both pre- andpolymerized organic matrix.

FIG. 13 shows magnified DSC traces of the composite before (solid) andafter (short dash) thermal crosslinking at 140° C. It can be seen thatthere are two broad exotherms, at about 120° C. and at about 190° C., inpre-polymerized matrix hybrid, which is possibly related to two-stepcuring of polyurethane network. The lower temperature exotherm (75°C.-150° C. range) may involve mostly curing with difunctional isocyanate(IPDI-DIPA), and hence the formation of higher molecular weight, linearpolyurethane, whereas the second exotherm (175° C.-210° C.) is a resultof the reaction with the cross-linker and a formation of a polyurethanenetwork. This is evidenced by the DSC trace of the composite aftercuring at 140° C. (short dash). The trace shows no endothermic peaks atup to about 175° C., which provides evidence that the first step ofcuring (formation of higher molecular weight polyurethane chains) wascompleted during curing at 140° C. The endotherm signal at 175° C.-200°C. indicates that not all reactive components have reacted. Thus, theDSC after curing at 140° C. provides strong evidence that fullycross-linked polyurethane matrix can be prepared as the composite isheated to 175° C. and above, as it shows that below that temperature notall blocked isocyanate groups undergo deprotection.

In addition decomposition temperature obtained from DSC traces of pureblocked isocyanates, IPDI-DIPA and PPFI-DIPA (not shown), correspondwell to reaction endotherms observed in pre-polymerized composite. TheDSC of pure PPFI-DIPA shows that the release of the last (third)isocyanate group (that allows the PPFI-DIPA to act as a cross-linker)does not start until about 175° C. and has its minimum about 190° C.(short dash). Both temperatures overlap respectively with the onset andmaximum temperature of the second reaction endotherm observed in pre-and post-polymerized composites (solid and short dash) in FIGS. 12 and13.

In the description above and in the claims, numerical ranges areinclusive of the end points of the range. For example, “an averagediameter between 0.1 μm and 500 μm,” includes 0.1 m and 500 m.Similarly, ranges represented by a dash (e.g., 50%-99%) are inclusive ofthe end points of the ranges.

The foregoing describes the instant invention and its certainembodiments. Numerous modifications and variations in the practice ofthis invention are expected to occur to those skilled in the art. Forexample, while the above specification describes electrolytes andcathodes for alkali ion or alkali metal batteries, the compositionsdescribed may be used in other contexts. Further, the batteries andbattery components described herein are no limited to particular celldesigns. Such modifications and variations are encompassed within thefollowing claims.

The invention claimed is:
 1. A composition comprising: a solid cross-linked polymer matrix that has substantially no added salts and is non-ionically conductive; and ionically conductive inorganic particles constrained in the solid cross-linked polymer matrix, wherein the ionically conductive inorganic particles are lithium-containing inorganic particles or sodium-containing inorganic particles, wherein the composition has an ionic conductivity of at least 10⁻⁴ S/cm at room temperature and wherein the composition is characterized by exhibiting the same ionic conductivity under applied pressures of 0.1 MPa and 95 MPa.
 2. The composition of claim 1, wherein contacting ionically conductive inorganic particles form ionically conductive pathways throughout the composition.
 3. The composition of claim 1, wherein the ionically conductive inorganic particles embedded in the solid cross-linked polymer matrix exhibit the same crystallization temperature as pristine ionically conductive particles.
 4. The composition of claim 1, wherein the ionically conductive inorganic particles comprise partially crystalline particles.
 5. The composition of claim 1, wherein the ionically conductive inorganic particles comprise amorphous particles.
 6. The composition of claim 1, wherein the ionically conductive inorganic particles comprise isotropic conductive paths.
 7. The composition of claim 1, wherein the ionically conductive inorganic particles comprise ceramic particles.
 8. The composition of claim 1, wherein the ionically conductive inorganic particles are lithium-containing inorganic particles.
 9. The composition of claim 1, wherein the ionically conductive inorganic particles are sodium-containing inorganic particles.
 10. The composition of claim 1, wherein the solid cross-linked polymer matrix comprises a polyolefin, a polysiloxane, polystyrene, a cyclic olefin polymer, poly(urethane), a poly(ureaurethane), poly(thiourethane), a poly(acrylate), a poly(methacrylate), a poly(maleimide), poly(acrylamide), a poly(methacrylamide), or a cured epoxy resin.
 11. The composition of claim 1, wherein the ionically conductive inorganic particles are sulfides.
 12. The composition of claim 1, wherein the ionically conductive inorganic particles are oxides.
 13. A composition comprising: a solid cross-linked polymer matrix that has substantially no added salts and is non-ionically conductive; ionically conductive inorganic particles constrained in the solid cross-linked polymer matrix, the ionically conductive inorganic particles comprising isotropic conductive paths; wherein the composition has an ionic conductivity of at least 10⁻⁴ S/cm at room temperature, wherein the ionically conductive inorganic particles embedded in the solid cross-linked polymer matrix exhibit the same crystallization temperature as pristine ionically conductive particles.
 14. The composition of claim 13, wherein contacting ionically conductive inorganic particles form ionically conductive pathways throughout the composition.
 15. The composition of claim 13, wherein the ionically conductive inorganic particles comprise partially crystalline particles.
 16. The composition of claim 13, wherein the ionically conductive inorganic particles comprise amorphous particles.
 17. A composition comprising: a solid cross-linked polymer matrix that has substantially no added salts and is non-ionically conductive; ionically conductive inorganic particles constrained in the solid cross-linked polymer matrix, the ionically conductive inorganic particles comprising isotropic conductive paths; wherein the composition has an ionic conductivity of at least 10⁻⁴ S/cm at room temperature.
 18. The composition of claim 17, wherein contacting ionically conductive inorganic particles form ionically conductive pathways throughout the composition.
 19. The composition of claim 17, wherein the ionically conductive inorganic particles comprise partially crystalline particles.
 20. The composition of claim 17, wherein the ionically conductive inorganic particles comprise amorphous particles.
 21. The composition of claim 17, wherein the ionically conductive inorganic particles comprise glass-ceramic particles. 